2003MNRAS.343..353S

The Capodimonte-Sternberg-Lens candidate no. 1 is an extragalactic double source detected in the Osservatorio Astronomico di Capodimonte - Deep Field. It can be interpreted either as the chance alignment of two identical galaxies at z = 0.46 or as the first case of gravitational lensing by a cosmic string. Extensive modelling shows in fact that cosmic strings are the only type of lens which (at least at low angular resolution) can produce undistorted double images of a background source. We propose an experimentum crucis to disentangle these two possible explanations. If the lensing by a cosmic string should be confirmed, it would provide the first measurements of energy scale of symmetry breaking and of the energy scale of grand unified theory.